In a traditional machining system of this category wherein the machining operation is performed while a workpiece is immersed in a machining fluid filled in a work pan, the work pan must be large enough to be able to accommodate therein the whole of the lower arm, as can be seen in, for example, U.S. Pat. No. 4,029,929 and U.S. Pat. No. 4,367,129. It is therefore liable to disadvantageously make the whole system large in size through inevitable enlarging of the work pan.